From DE-A-102 61 284, a rotary operating element is known which upon application of a force can be moved along its rotational axis. Said operating element comprises a toothed portion arranged in engagement with a gear so that the rotation of the operating element will be transmitted onto the gear. In this configuration, the rotational axis of the gear is disposed parallel to, and laterally of, the rotational axis of the operating element. This measure allows for a movement of the operating element along its rotational axis. Said toothed portion preferably forms a gear itself, thus allowing for a full rotation of the operating element. However, a disadvantage of this known operating element resides in that the rotation and the movement of the operating element in the axial direction are realized by the cooperation of a plurality of gears and the construction will thus be overly complex.
Known from DE-A-102 12 992 is a rotary operating element comprising a immobile inner portion and a rotatable ring element and respectively sleeve element as an outer portion, the latter being supported on said inner portion by means of a rolling bearing.